Evaporation is a process of putting a substance to be filmed in vacuum for evaporation or sublimation so that the substance is separated out on a surface of a workpiece or a substrate. Heating an evaporation material and coating the same on the substrate in a vacuum is referred to as a vacuum evaporation, or vacuum coating. The vacuum coating is applied to manufacturing processes of devices (such as a display panel) in most cases.
In the evaporation process of a display panel, a mask is used for shielding a particular region of a glass substrate so that an evaporation material is separated out in a non-shielding region to form a film. In theory, the surface of the mask is parallel to the glass substrate, and in this case, an evaporation result completely corresponds to the mask and conforms to a design.
However, in reality, since an edge of the mask is fixed to a support frame and the mask is extremely thin (the thickness of the mask is dozens of microns), the deformation of the mask caused by its own gravity action cannot be ignored. Under the effect of the deformation, a film obtained on the glass substrate deviates from an expected situation, so that the evaporation effect of the evaporating device is poor. In addition, in the process of fixing the mask by the evaporating device, when variation of force applied to the mask in a vertical direction is large, the mask may hit against the glass substrate at a high speed, which not only may damage the glass substrate and the mask, but also may result in a problem of scratch of a photo-spacer (PS) on the glass substrate.